Dynamical transition in the wigner solid on a liquid helium surface

We have observed a dynamical transition in the Wigner solid on liquid He4. The ac Corbino conductivity σxx jumps abruptly at certain input voltage and shows hysteretic behavior. The threshold input voltage Vth has dependences on the magnetic field B perpendicular to the surface, frequency ω, electron density ns, and electric field E as VthB-0.8ω-1ns1.5E. We attribute the conductivity jump to the collective sliding of the electrons out of the periodic deformation of the He surface.